Magnetic recording medium and magnetic memory apparatus

ABSTRACT

Disclosed is a magnetic memory apparatus which comprises a patterned magnetic recording medium in which multilayered films each having a first magnetic layer, a nonmagnetic metal layer or a nonmagnetic insulating layer and a second magnetic layer deposited discretely on a conductive electrode layer formed on a substrate, and a cantilever array having a plurality of cantilevers each having a conductive chip at its distal end. This provides a magnetic solid memory apparatus that has a large memory capacity and a super fast transfer rate, the merits of a hard disk apparatus, and a nanostructure and low power consumption, which are the merits of a semiconductor memory.

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT

1. Field of the Invention

The present invention relates to a magnetic recording medium and amagnetic memory apparatus using the same, and, more particularly, to apattern type magnetic recording medium having multilayerednanostructures having a magnetoresistance effect laid out discretely anda magnetic memory apparatus which writes and reads information from therecording medium using a cantilever array.

2. Description of the Related Art

The surface recording density of magnetic disk apparatuses is everincreasing and is expected to reach 100 gigabits per inch in 2003. Thepresent in-plane recording system, however, has a problem that as thebit length to write becomes shorter, magnetic signals written on arecording medium are vanished by thermal fluctuation, which stands inthe way of increasing the surface recording density. Attention is paidto a perpendicular recording system which writes magnetic signals in adirection perpendicular to the recording medium as a solution to thisproblem. In particular, as the perpendicular recording system which usesa perpendicular recording medium having a soft-magnetic backing layer asa recording medium and uses a single-pole head to write information hasa high resistance to a thermal fluctuation and can generate a strongrecording magnetic field, the perpendicular recording system is apromising future perpendicular recording system for super high density.

For example, FD-08 in the 8th Joint MMM-Intermag Conference held at SanAntonio in America in January 2001 has reported perpendicular recordingwith a surface recording density of 60 gigabits per square inch (seeNon-patent Document 1).

In the perpendicular recording system, as recording bits become smalleras the surface recording density increases, the area of the floatingsurface of the single-pole head to be used in writing information whichfaces a magnetic recording medium should be made smaller. As the area ofthe floating surface of the single-pole head is reduced, however, theintensity of the magnetic field that can be generated is reduced ininversely proportional to that area. This results in insufficientrecording. A first solution to this shortcoming is to increase thesaturation magnetic flux density Bs of the magnetic substance thatconstitutes the single-pole head. As the theoretical limit of thesaturation magnetic flux density Bs of the magnetic substance is 3.0tesla, which is merely 1.5 times the theoretical limits of materialsavailable at present and cannot cope with the future higher density.

The conventional magnetic recording has been done by inverting themagnetization of a magnetic recording medium using the magnetic fieldgenerated by the induction type magnetic head which floats and runs overthe magnetic recording medium. A recent magnetic random access memory(MRAM) which is a possible substitute for the conventional dynamicrandom access memory (DRAM) employs a recording system which inverts themagnetization of one of tunneling magnetoresistance effect (TMR)elements having a multilayered structure of a magnetic film/non-magneticinsulating film/magnetic film by using a combined magnetic field formedby the current that runs through two metal lines laid on and under thisTMR element, perpendicular to each other (see, for example, PatentDocument 1: U.S. Pat. No. 5,734,605). It is however pointed out that theMRAM has a shortcoming that as the size of TMR elements is made smallerfor larger memory capacity, the size of the magnetic field needed toinvert magnetization becomes larger, requiring that a lot of currentshould flow through the metal lines. This leads to an increase in powerconsumption and eventually damages the lines. Those facts suggest thatthe magnetic disk apparatus as well as the MRAM suffer limitation toincreasing the density as long as the magnetization inversion systemusing a magnetic field is employed.

As a scheme of inverting magnetization without using a magnetic field, amagnetic recording system has been proposed which makes magneticrecording by causing the current to flow to a magnetic recording mediumfrom a probe having a conductive chip and heating the portion where thecurrent has run (see, for example, Patent Document 2: Japanese PatentLaid-Open No. Hei 5-206146).

There is an empirical report on a recording system which forms pillarsof 130 nm in diameter each including a multilayered film of Co/Cu/Cobetween two Cu electrodes and inverts the magnetization of the Co layerby letting the current flow in the pillars (see, for example, Non-patentDocument 2: Physical Review Letters, Vol. 84, No. 14, pp. 3149-3152(2000)).

Several ideas of constructing a super high density writing/readingapparatus without using magnetic recording have also been proposed. Oneof the proposed ideas is a recording system which uses an array of 32×32cantilevers 102 each having a heater formed at its distal end andpolycarbonate and makes recording by heating the heater at the distalend of a cantilever and pressing the heater against the polycarbonate todeform the polycarbonate, thereby forming holes therein (see, forexample, Non-patent Document 3: Applied Physics Letters, Vol. 77, No.20, pp. 3299-3301 (2000)).

The conventional proposals however have the following problems.

In the system that makes magnetic recording by causing the current toflow to a magnetic recording medium from a probe and heating thecurrent-flown portion, for example, magnetic recording is done by theJoule heat of the supplied current, so that the inversion ofmagnetization takes time. The system cannot therefore ensure as fastrecording as achieved by the conventional magnetic disk apparatus andMRAM.

The recording system that forms pillars of 130 nm in diameter eachincluding a multilayered film of Co/Cu/Co and inverts the magnetizationof the Co layer by letting the current flow in the pillars requires acurrent density of about 3×10⁷ (A/cm²) for recording. In case where sucha large current is provided from the metal lines of the conventionalMRAM, therefore, the current density that even lines of a tungsten-basedmaterial which has a large durability to the current can withstand isabout 1×10⁷ (A/cm²) so that the cross-sectional area of the lines cannotbe made smaller than a 150-nm square. This stands in the way ofincreasing the density. In addition, because the system requires that acurrent of a high current density should run through long lines, thesystem has a reliability problem.

As the system that makes recording by heating the heater at the distalend of a cantilever and pressing the heater against polycarbonate todeform the polycarbonate and form holes therein also uses heat andsuffers a slow writing speed of several tens of microseconds. While thisprior art proposes a way of increasing the writing speed by parallelwriting with a total of 1024 cantilevers, the writing speed of eachcantilever is slow which, it seems, makes it very hard to achieve thefast recording done by the magnetic disk apparatus.

OBJECT AND SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to overcome theaforementioned problems using the following means.

A magnetic memory apparatus comprising:

a patterned magnetic recording medium in which multilayerednanostructures each having a first magnetic layer, a nonmagnetic metallayer or a nonmagnetic insulating layer and a second magnetic layerlaminated in that order on a conductive electrode layer formed on asubstrate are laid out apart from one another at substantially evenpitches; and

a cantilever array in which cantilevers having conductive chips atdistal ends are laid out in an array and apart from one another in sucha way as to be associated with the nanostructures, whereby informationis written or read by a current supplied from that one of the conductivechips which is associated with a desired one of the nanostructures asthat conductive chip is put in contact with the desired nanostructure.

Particularly, the magnetic recording medium may further comprise meansfor fixing the direction of magnetization of one of magnetic layersconstituting the multilayered film showing a tunneling magnetoresistance(TMR) effect or the multilayered film showing a giant magnetoresistance(GMR) effect, e.g., the first magnetic layer or the second magneticlayer, to one direction. In particular, an antiferromagnetic film isused as the fixing means.

Further, as a magnetic recording medium, a patterned magnetic recordingmedium is used in which multiple nanostructures each comprising amultilayered film having a lamination of a multilayered film showing aTMR magnetoresistance effect and a multilayered film showing a GMReffect are surrounded by insulators in such a way as to be laid outapart from one another at substantially even pitches and are provided ona conductive electrode layer formed on a substrate. Particularly, it issuitable to form the multilayered film showing both the TMR effect andGMR effect by laminating a first magnetic layer, a nonmagnetic electrodelayer, a second magnetic layer, a nonmagnetic insulating layer and athird magnetic layer in that order, and use the second magnetic layerboth in the TMR effect multilayered film and the GMR effect multilayeredfilm. Further, the magnetic recording medium may further comprise meansfor fixing the direction of magnetization of the third magnetic layer toone direction. Furthermore, an antiferromagnetic film is used as themeans for fixing the direction of magnetization to one direction.

In the above-described magnetic memory apparatus of the presentinvention, digital information is written by inverting magnetizationwith 1 being a state where a resistance of the multilayered film is highwhile 0 is a state where the resistance is low, using a current suppliedfrom that one of the conductive chips which is associated with a desiredone of the nanostructures (pillars) as that conductive chip is put incontact with the desired nanostructure. Further, a signal is read bycausing a current whose value is smaller than that of a current by whichmagnetization of the multilayered film is inverted to flow from theconductive chip and detecting the level of the resistance of eachmultilayered pillar.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view showing the schematic general structure ofone example of a magnetic memory apparatus embodying the presentinvention;

FIG. 1B is a diagram showing one cantilever in FIG. 1A and a part of amagnetic recording medium in enlargement;

FIG. 1C is a schematic plan view of the magnetic recording medium;

FIG. 2 is a diagram illustrating the principle of the writing/readingoperation of the magnetic memory apparatus in FIG. 1A;

FIG. 3A is a perspective view showing a second example of the magneticrecording medium according to the invention;

FIG. 3B is a plan view;

FIGS. 4A and 4B are diagrams showing a third example of the magneticrecording medium according to the invention;

FIG. 5A is a plan view of a cantilever used in the invention;

FIG. 5B is a diagram showing a part extracted from a cantilever arrayused in the invention;

FIG. 6 is a diagram illustrating a system of selecting cantilevers whichperform writing and reading operations; and

FIGS. 7A to 7D are process diagrams illustrating one example of a methodof fabricating a patterned magnetic recording medium according to theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described belowwith reference to the accompanying drawings. FIGS. 1A to 1C show oneexample of a magnetic memory apparatus according to the invention. FIG.1A is a perspective view showing the schematic general structure of themagnetic memory apparatus according to the invention, FIG. 1B is adiagram showing one of cantilevers of the magnetic memory apparatus anda part of a magnetic recording medium in enlargement, and FIG. 1C is aplan view showing the schematic structure of the magnetic recordingmedium.

In FIGS. 1A to 1C, “101” is a cantilever array, “102” denotescantilevers, “103” is a magnetic recording medium, “104” is a cellselection/signal processing section, and “105” is a conductive chipportion. Further, “106” is a conductive electrode layer, “107” is afirst magnetic layer, “108” is a nonmagnetic metal layer or nonmagneticinsulating layer and “109” is a second magnetic layer.

Each multilayered film which is the lamination of the layers 107, 108and 109 (hereinafter referred to as “lamination of 107, 108 and 109”)constitutes a pillar-like nanostructure (hereinafter referred to as“pillar”) 114. Those multilayered pillar-like nanostructures 114 arelaid out apart from one another at substantially even pitches as shownin FIG. 1C. “110” denotes an insulating portion formed between thepillars 114, “111” is a substrate, “112” is a magnetic cap layer and“113” is a magnetic base metal. In FIG. 1C, “114” indicates a singlepillar.

The materials for the two magnetic films indicated by “107” and “109”can be selected from Co, Fe, Ni and their alloys. In case where “108” isa nonmagnetic metal layer, the lamination of 107, 108 and 109constitutes a multilayered pillar which demonstrates a giantmagnetoresistance (GMR) effect and Cu, for example, is a desirablematerial for this nonmagnetic metal layer. In case where “108” is anonmagnetic insulating layer, the lamination of 107, 108 and 109constitutes a multilayered pillar which demonstrates a tunnelingmagnetoresistance (TMR) effect and an oxide containing an element, suchas Al, Ta, Mg, Hf or Zr, or a nitride containing an element, such as Alor Ti, can be used as the material for this nonmagnetic insulatinglayer.

It is to be noted that FIGS. 1A to 1C illustrate the schematic structureof the cantilever array and patterned magnetic recording medium whichare used in the invention and the numbers of the cantilevers and themultilayered pillars both illustrated are omitted, not to mention thatthe magnifications of FIGS. 1A to 1C are not the same. The same is trueof the other diagrams.

FIG. 2 is a diagram illustrating the principle of the writing/readingoperation of the magnetic memory apparatus in FIGS. 1A to 1C. As shownin FIG. 1B, the conductive chip 105 provided at the distal end of thecantilever 102 is made in contact with a desired multilayered pillar anda voltage is applied there to let a current flow. A negative current islet to flow first and as the current value is changed in the positivedirection from the negative direction, the direction of magnetization ofone of the two magnetic layers 107 and 109 whose directions ofmagnetization have been in the same direction so far is shifted by 180degrees at a given current value I⁺ so that the directions ofmagnetization become antiparallel to each other. When the directions ofmagnetization become antiparallel to each other, the GMR effectincreases the resistance. This state is a “1” state.

On the other hand, a positive current is let to flow first and as thecurrent value is changed in the negative direction from the positivedirection, the direction of magnetization of one of the two magneticlayers 107 and 109 whose directions of magnetization have beenantiparallel to each other so far is shifted by 180 degrees at a givencurrent value I⁻ so that the directions of magnetization become thesame. When the directions of magnetization become the same, theresistance decreases to the original value. This state is a “0” state.That is, the current-resistance curve has a so-called hysteresis asshown in FIG. 2.

In the case of a sample where the multilayered pillar in FIG. 1B had anarea of a 20-nm square, the magnetic layers 107 and 109 were formed ofCoFe and the nonmagnetic metal layer 108 was formed Cu, the value of I⁺was 80 μA and the value of I⁻ was 150 μA. It is desirable that theabsolute values of the currents should be set to be double the absolutevalues of I⁺ and I⁻ (+160 μA and −300 μA respectively in the case of apillar with a 20-nm square) in performing the actual writing anddeleting operations, while the current value I should be set to liebetween I⁺ and I⁻ in performing the reading operation.

FIGS. 3A and 3B are diagrams showing the second example of the magneticrecording medium used in the invention. FIG. 3A is a perspective viewshowing one cantilever and a part of a magnetic recording medium, inenlargement, according to the embodiment, and FIG. 3B is a schematicplan view of the magnetic recording medium.

In the embodiment, an antiferromagnetic layer 301 which fixes thedirection of magnetization of the first magnetic layer 107 to onedirection is provided under the magnetic layer 107. It is suitable touse, for example, an alloy having Mn and Pt as the bases or an alloyhaving Mn and Ir as the bases for the antiferromagnetic layer.

Because the direction of magnetization of the first magnetic layer 107is fixed to one direction in the embodiment, it is mainly the secondmagnetic layer 109 whose direction of magnetization changes, thusincreasing the output of a read signal and the stability. Although theantiferromagnetic layer 301 is provided under the first magnetic layer107 in FIGS. 3A and 3B, the antiferromagnetic layer 301 may be providedabove the second magnetic layer 109 in which case even when thedirection of magnetization of the second magnetic layer 109 is fixed toone direction, the same effect as provided by the case where theantiferromagnetic layer is provided under the first magnetic layer 107can be attained.

FIGS. 4A and 4B are diagrams showing the third example of the magneticrecording medium which is used in the invention. In FIG. 4A, a firstmagnetic layer 401, a nonmagnetic insulating layer 402, a secondmagnetic layer 403, a nonmagnetic metal layer 404 and a third magneticlayer 405 are laminated on a magnetic base metal 113. In thispillar-like nanostructure, the first magnetic layer 401, the nonmagneticinsulating layer 402 and the second magnetic layer 403 constitute amultilayered portion which demonstrates the TMR effect and the secondmagnetic layer 403, the nonmagnetic metal layer 404 and the thirdmagnetic layer 405 constitute a multilayered portion which demonstratesthe GMR effect. This embodiment is a multilayered pillar-likenanostructure which has the TMR effect and GMR effect combined together.

What is more, the second magnetic layer serves as both the magneticlayer of the TMR portion and the GMR portion in the embodiment. As theTMR effect is greater than the GMR effect and the resistance of the GMRportion is greater than the resistance of the GMR portion by the orderof two to four digits, most of the change in resistance is obtained fromthe TMR portion.

In the case of the structure in FIG. 4A, to use a large change in theresistance of the TMR portion, the magnetic layer whose direction ofmagnetization is inverted by the supply of the current should be thesecond magnetic layer 403. To fulfill the requirement, the coerciveforce of the second magnetic layer 403 should be made lower than thecoercive forces of the first and third magnetic layers and it ispreferable to take measures, such as using a material with an extremelygood soft magnetic characteristic like an alloy of Ni80Fe20 for thesecond magnetic layer and using a material with a relatively highcoercive force like an alloy of Co and Fe for the third magnetic layer.

To meet the issue, antiferromagnetic layers 406 and 407 for fixing thedirection of magnetization of the first and third magnetic layers areprovided under the first magnetic layer 401 and above the third magneticlayer 405 in the structure in FIG. 4B. As the materials for theantiferromagnetic layers, the aforementioned alloy having Mn and Pt asthe bases, alloy having Mn and Ir as the bases or the like is used. Asthis structure can fix the direction of magnetization of the first andthird magnetic layers to one direction closely, various materials usedin the first embodiment can be used for the magnetic layers. Therefore,the first magnetic layer 401 and the third magnetic layer 405 act as afixed layer with its magnetization fixed and the magnetic layer 403 actsas a free layer whose direction of magnetization turns in accordancewith an external magnetic field in the multilayered nanostructure inFIG. 4B.

The following will more specifically discuss the characteristics of thematerial structures with the pillar-like nanostructure taken as anexample shown in FIG. 4B. Cu was used for the magnetic base metal 113, aPtMn alloy was used for the antiferromagnetic layer 406, a CoFe alloywas used for the first magnetic layer 401, Al oxide was used for thenonmagnetic insulating layer 402, a CoFe alloy was used for the secondmagnetic layer 403, Cu was used for the nonmagnetic metal layer 404, aCoFe alloy was used for the third magnetic layer 405, an IrMn alloy wasused for the antiferromagnetic layer 407 and Cu was used for the uppercap layer 112.

The thickness of the Al oxide layer 402 that determines the resistanceof this structure was set to 1.2 nm, the resistance of the multilayeredstructure extending from the cap layer 112 to the base metal 113 perarea was about 4 Ω·μm². As this multilayered structure is formed into apillar of a 20-nm square, the resistance of the actual pillar portion is10 kΩ.

When the current of 200 μA was let to flow in this multilayered pillar,the resistance became 12 kΩ, increased by about 20%, and the writingstate changed to “1” from “0”. When the current of 200 μA was let toflow in the opposite direction, the resistance returned to the original10 kΩ and the writing state changed to “0” from “1”.

The power used in writing was 0.4 mW, significantly lower than the power(1 W or greater) needed in writing in the conventional hard diskapparatus or the power (several mW) per single memory cell in a1-megabit MRAM that had been reported already. This apparent shows thatthe system of the embodiment demonstrates a large effect on powerreduction.

The states of “0” and “1” were discriminated by supplying the current of20 μA in the multilayered pillar from the conductive chip 105 and anoutput difference of 40 mV was detected between the “0” and “1” states.Although this value is smaller than the output of 100 mV of the dynamicrandom access memories available as products at present, it is stillgreater than the output (1 to 2 mV) from a magnetic head mounted in thehard disk apparatus by more than one digit and can be detectedsufficiently.

FIG. 5A is a plan view of the cantilever that is used in the invention.“501” is a conductive chip (formed at the back of a cantilever) providedat the distal end of the cantilever, “502” is a line for leading thecurrent to the conductive chip 501, “503” and “504” are piezoelectricelements 503 and 504 for detecting and controlling the attitude, “505”and “506” are lines for supplying a voltage to the piezoelectricelements 503 and 504 respectively and detecting the outputs thereof, and“507” is a lever portion whose middle portion is hollowed to improve theresonance frequency.

FIG. 5B shows a part extracted from the cantilever array used in theinvention. The cantilever array has an array of cantilevers each havingthe conductive chip 501 at its distal end in such a way as to beassociated with a predetermined nanostructure in the multilayerednanostructures (multilayered pillars) discretely laid out as a recordingmedium.

In the diagram, “508” is a line provided to supply a current to theconductive chip provided at the distal end of the cantilever 507, and“509”, “510”, “511” and “512” are lines for applying a voltage to thepiezoelectric elements 503 and 504. The lines 509 and 511 apply avoltage to the piezoelectric element 503 and one end of the line 505 isconnected to the lines 509 and 511 orthogonal to each other.

The lines 510 and 512 apply a voltage to the piezoelectric element 504and one end of the line 506 is connected to the lines 510 and 512orthogonal to each other.

Hereinafter, the line 509 is referred to as a bit line 1, the line 510is referred to as a bit line 2, the line 511 is referred to as a wordline 1 and the line 512 is referred to as a word line 2. Although thelines drawn only for the single upper left cantilever in FIG. 5B,similar lines are laid out for all the other cantilevers.

FIG. 6 is a diagram illustrating a system of selecting desiredcantilevers which perform writing and reading operations. Here, “601” isa line which supplies a voltage to the word line 1 (511 in FIG. 5B),“602” is a line which supplies a voltage to the word line 2 (512 in FIG.5B), “603” is a line which supplies a voltage to the bit line 1 (509 inFIG. 5B), “604” is a line which supplies a voltage to the bit line 2(510 in FIG. 5B), and “605” is a common ground.

In FIG. 6, only two of column select switches connected to the lines 601and 602, which are indicated by (a) in the diagram, are set ON. Thisallows a potential V to be given only to the word lines 608 and 609particularly selected.

Meanwhile, only two of row select switches connected to the lines 603and 604, which are indicated by (b) in the diagram, are connected to theground, and only the bit lines 606 and 607 particularly selected are setto the ground potential. The potential V is given to all of the otherbit lines. This allows the potential difference V to be given only totwo piezoelectric element indicated by (c) in the diagram. The potentialdifference cause the piezoelectric element to deform and the conductivechip of the cantilever on which the piezoelectric element is mountedcontacts the desired multilayered pillar of the recording medium.

Then, the current is supplied to the desired, selected multilayeredpillar via the line 502, so that the writing/reading operation isperformed. The force to be applied to the cantilever to make a contactto the recording medium can be controlled by the potential V to beapplied. In case where the attitude of the cantilever is deformed rightor left by the upheavals of the recording medium, the attitude can becontrolled by setting the potential to be applied to the lines 601 and602 and the potential to be applied to the lines 603 and 604 not beequal to each other but in such a way as to have a difference to adjustthe balance of the force to be applied to the cantilever 507.

The performance of the magnetic memory apparatus according to theinvention will be discussed below. The time needed for such motion ofthe cantilever depends on the resonance frequency of the cantilever andthe response speed of the piezoelectric element. In case where thelength L and the width W of each cantilever are set to 5 μm in FIGS. 5Aand 5B, for example, the response speed is equal to or lower than 0.1μs, ensuring a sufficiently fast response. The speed needed forinverting the magnetization by the supply of the current from theconductive chip 501 provided at the distal end of the cantilever and thetime needed to detect a read signal are both equal to or lower than 10ns.

Therefore, the transfer rate of the magnetic memory apparatus of theinvention is equal to or higher than 10 Mbps per single cantilever sothat if 1000 cantilevers are laid out and parallel transfer isperformed, the overall transfer rate of the apparatus becomes 10 Gbps,which ensures faster transfer than the existing magnetic disk apparatus.With regard to the recording capacity of the memory, in case wheremultilayered pillars each of a 20-nm square are laid outtwo-dimensionally at pitches of 20 nm as shown in FIGS. 1A to 1C, it ispossible to achieve a large capacity of 100 GB, more than 100 times thecapacity of flash memories available as products at present, on a mediumchip of a 2.3-cm square.

FIGS. 7A to 7D are process diagrams illustrating one example of a methodof fabricating a patterned magnetic recording medium according to theinvention. First, as shown in FIG. 7A, an electron beam writing resist709 is patterned into a desired shape using an electron beam writingscheme and a master 702 is patterned by ion milling or the like using Arions 701. The pattern to be formed is line patterns having a width of 5nm to 30 nm laid out apart from one another at even pitches of 5 nm to30 nm and horizontally and vertically in the orthogonal fashion, and ismore preferably line patterns having a width of 20 nm or less.

Subsequently, a multilayered film 705 which demonstrates the desired TMReffect and/or GMR effect and which becomes pillar-like nanostructurelater is deposited on a conductive electrode layer 706, as shown in FIG.7B. Then, an ultraviolet-cured type resist resin 704 is formed on themultilayered film 705 and the patterned master 702 is pressed againstthe resist resin 704 while irradiating ultraviolet rays 703 to transferthe pattern of the master onto the resist resin 704.

Next, as shown in FIG. 7C, the multilayered film 705 is etched using areactive ion etching gas 707 to form multilayered pillar-likenanostructures laid out discretely, after which the resist resin 704 isremoved.

Finally, as shown in FIG. 7D, a non-magnetic insulating material 708 isdeposited in such a way as to be filled between the pillar-likenanostructures and the medium is planarized by chemical mechanicalpolishing (CMP) which completes the fabrication of the medium. Thismethod can fabricate a patterned recording medium in which multilayeredpillar-like nanostructures each of a square of 5 nm to 30 nm, surroundedby the insulating material 708 and laid out at even pitches of 5 nm to30 nm are formed on the conductive electrode layer.

As described above, the invention can provide a magnetic memoryapparatus that has a large memory capacity and a super fast transferrate, which are the merits of a hard disk apparatus, and a nanostructureand low power consumption, which are the merits of a semiconductormemory.

1. A magnetic memory apparatus comprising: a patterned magneticrecording medium in which multilayered nanostructures each having afirst magnetic layer, a nonmagnetic metal layer or a nonmagneticinsulating layer and a second magnetic layer laminated in that order ona conductive electrode layer formed on a substrate are laid out apartfrom one another at substantially even pitches; and a cantilever arrayin which cantilevers having conductive chips at distal ends are laid outin an array and apart from one another in such a way as to be associatedwith said nanostructures, whereby information is written or read by acurrent supplied from that one of said conductive chips which isassociated with a desired one of said nanostructures as that conductivechip is put in contact with said desired nanostructure.
 2. The magneticmemory apparatus according to claim 1, wherein the patterned magneticrecording medium includes pillar-like nanostructures each comprising amultilayered film showing a tunneling magnetoresistance effect or amultilayered film showing a giant magnetoresistance effect aresurrounded by insulators in such a way as to be laid out apart from oneanother at substantially even pitches and are provided on a conductiveelectrode layer formed on a substrate.
 3. A patterned magnetic recordingmedium in which pillar-like nanostructures each comprising amultilayered film having a lamination of a multilayered film showing atunneling magnetoresistance effect and a multilayered film showing agiant magnetoresistance effect are surrounded by insulators in such away as to be laid out apart from one another at substantially evenpitches and are provided on a conductive electrode layer formed on asubstrate.
 4. A patterned magnetic recording medium in which pillar-likenanostructures each comprising a multilayered film showing a tunnelingmagnetoresistance effect or a multilayered film showing a giantmagnetoresistance effect are surrounded by insulators in such a way asto be laid out apart from one another at substantially even pitches andare provided on a conductive electrode lever formed on a substrate,wherein said multilayered film showing said tunneling magnetoresistanceeffect comprises a multilayered film having a first magnetic layer, anonmagnetic insulating layer and a second magnetic layer laminated inthat order, said multilayered film showing said giant magnetoresistanceeffect comprises said second magnetic layer, a nonmagnetic metal layerand a third magnetic layer laminated in that order, and said secondmagnetic layer constituting said multilayered film showing saidtunneling magnetoresistance effect serves as said second magnetic layerconstituting said multilayered film showing said giant magnetoresistanceeffect.
 5. The magnetic memory apparatus according to claim 2, where thepatterned magnetic recording medium comprising means for fixing adirection of magnetization of one of magnetic layers constituting saidmultilayered film showing said tunneling magnetoresistance effect orsaid multilayered film showing said giant magnetoresistance effect toone direction.
 6. The patterned magnetic recording medium according toclaim 4, comprising means for fixing a direction of magnetization ofsaid third magnetic layer to one direction.
 7. The magnetic memoryapparatus according to claim 5, wherein the means for fixing saiddirection of magnetization to one direction is an antiferromagneticfilm.
 8. A magnetic memory apparatus comprising: a patterned magneticrecording medium in which nanostructures each comprising a multilayeredfilm showing a tunneling magnetoresistance effect and/or a multilayeredfilm showing a giant magnetoresistance effect are surrounded byinsulators in such a way as to be laid out apart from one another atsubstantially even pitches and are provided on a conductive electrodelayer formed on a substrate; and a cantilever array in which cantilevershaving conductive chips at distal ends are laid out in an array andapart from one another in such a way as to be associated with saidnanostructures, whereby information is written or read by a currentsupplied from that one of maid conductive chips which is associated witha desired one of said nanostructures as that conductive chip is put incontact with said desired nanostructure.
 9. A magnetic recording methodwhich uses a patterned magnetic recording medium in which nanostructureseach comprising a multilayered film showing a tunnelingmagnetoresistance effect and/or a multilayered film showing a giantmagnetoresistance effect are surrounded by insulators in such a way asto be laid out apart from one another at substantially even pitches andare provided on a conductive electrode layer formed on a substrate, anda cantilever array in which cantilevers having conductive chips atdistal ends are laid out in an array and apart from one another in sucha way as to be associated with said nanostructures, and writes digitalinformation by inverting magnetization with 1 being a state where aresistance of said multilayered film is high while 0 is a state wheresaid resistance is low, using a current supplied from that one of saidconductive chips which is associated with a predetermined one of saidnanostructures as that conductive chip is put in contact with saidpredetermined nanostructure.
 10. A signal reading method which uses apatterned magnetic recording medium in which nanostructures eachcomprising a multilayered film showing a tunneling magnetoresistanceeffect and/or a multilayered film showing a giant magnetoresistanceeffect are surrounded by insulators in such a way as to be laid outapart from one another at substantially even pitches and are provided ona conductive electrode layer formed on a substrate, and a cantileverarray in which cantilevers having conductive chips at distal ends arelaid out in an array and apart from one another in such a way as to beassociated with said nanostructures, end detects a level of a resistanceof each multilayered pillar by putting that one of said conductive chipswhich is associated with a predetermined one of said nanostructures incontact with said predetermined nanostructure and causing a currentwhose value is smaller than that of a current by which magnetization ofsaid multilayered film is inverted to flow from said conductive chip.11. The magnetic memory apparatus according to claim 1, wherein a numberof said multilayered nanostructures substantiality equals a number ofsaid cantilevers having the conductive chips at the distal ends thereof,wherein each respective one of said multilayered nanostructures isassociated with a predetermined differing respective one of saidcantilevers, whereby information is written or read by a currentsupplied from that one of said conductive chips which is associated witha desired one of said nanostructures as that conductive chip is put incontact with said desired nanostructure.
 12. The magnetic memoryapparatus according to claim 8, wherein a number of said multilayerednanostructures substantially equals a number of said cantilevers havingthe conductive chips at the distal ends thereof, wherein each respectiveone of said multilayered nanostructures is associated with apredetermined differing respective one of said cantilevers, wherebyinformation is written or read by a current supplied from that one ofsaid conductive chips which is associated with a desired one of saidnanostructures as that conductive chip is put in contact with saiddesired nanostructure.
 13. The magnetic memory apparatus according toclaim 9, wherein a number of said multilayered nanostructuressubstantially equals a number of said cantilevers having the conductivechips at the distal ends thereof, wherein each respective one of saidmultilayered nanostructures is associated with a predetermined differingrespective one of said cantilevers, whereby information is written orread by a current supplied from that one of said conductive chips whichis associated with a desired one of said nanostructures as thatconductive chip is put in contact with said desired nanostructure. 14.The magnetic memory apparatus according to claim 10, wherein a number ofsaid multilayered nanostructures substantially equals a number of saidcantilevers having the conductive chips at the distal ends thereof,wherein each respective one of said multilayered nanostructures isassociated with a predetermined differing respective one of saidcantilevers, whereby information is written or read by a currentsupplied from that one of said conductive chips which is associated witha desired one of said nanostructures as that conductive chip is put incontact with said desired nanostructure.